In an engine of a vehicle, for example, a torsional damper is attached to one end of a crankshaft to reduce a torsional vibration caused by a rotational fluctuation of the crankshaft. The torsional damper used in the engine of the vehicle is typically in the form of a damper pulley and transmits part of the power of the engine to auxiliary machinery, such as a water pump, a compressor of an air conditioner or the like, through a power transmission belt. The gap between the torsional damper and, for example, a through-hole of a front cover into which the crankshaft is inserted is sealed by an oil seal.
FIG. 21 is a partial cross-sectional view taken along an axis, schematically showing a conventional arrangement of a damper pulley and an oil seal of an engine of a vehicle. As shown in FIG. 21, a conventional damper pulley 100 includes a hub 101, a pulley 102, and a damper elastic body 103 disposed between the hub 101 and the pulley 102. The hub 101 includes a boss part 101a on the inner periphery side, a rim part 101b on the outer periphery side, and a disk part 101c connecting the boss part 101a and the rim part 101b to each other. The damper pulley 100 is fixed to a crankshaft 120 by a bolt 121 with the boss part 101a of the hub 101 fitted into one end part of the crankshaft 120.
In addition, to reduce the weight, some conventional damper pulleys 100 have a plurality of windows 101d as through-holes passing through the disk part 101c of the hub 101, circumferentially formed (for example, see Japanese Utility Model Application Publication No. 05-25049 and Japanese Patent Application Publication No. 2011-241891).